Many coffee shops and convenience stores serve an array of coffee products, from mild to strong coffees brewed from coffee beans grown in different areas of the world, each imparting a particular flavour and aroma. Due to the limited counter space available in these stores, only a small selection of coffees are served each day, as coffee pots, heat plates and coffee bean grinders occupy a significant portion of the counter space. This selection can include strong, mild or medium roast coffees brewed from a variety of coffee beans.
In addition to these “standard” coffees, a selection of flavoured coffees are also served. Examples of such flavours include amaretto almond, French Vanilla and Irish cream. One method of providing flavoured coffees is to obtain flavoured coffee beans with the flavouring infused into the beans, and grinding them for brewing a pot of the flavoured coffee. Another method is to use pre-packaged, ground flavoured coffee. A third method is to stock a selection of flavour syrups that can be directly added to any regular cup of coffee by the server. This technique provides more flexibility since the flavour can be added to any standard coffee.
However, because separate grinders are required for grinding standard coffee beans and flavoured coffee beans to ensure that the standard coffee bean grinders are free from contamination from flavoured grounds, valuable counter space is taken up and additional cost is incurred by the extra grinder. Furthermore, flavoured coffees tend to stew in their pots for a relatively long period of time since they may not be as popular as the non-flavoured coffees. Those of skill in the art are well aware that coffee left standing on a heat plate for too long is unpalatable due to poor taste. Therefore, additional cost is incurred, as unsold flavoured coffee must be thrown out in favour of freshly brewed flavoured coffee. Although use of pre-packaged flavoured coffee obviates the need for an additional grinder, the problem with limited counter space and aged coffee persists. Furthermore, the consumer perception that pre-packaged coffee cannot be as fresh as freshly ground coffee tends to curb consumers from purchasing pre-packaged, flavoured coffee.
Bottles of flavoured liquids, or syrups, are easily stored upon shelves and countertops, and a wide selection of flavours can be made available to the consumer. Unfortunately, consistency of flavour between different servings is difficult to achieve because the dose of syrup added to each cup of coffee is subject to human error. Furthermore, the optimal dose of syrup changes for different sized cups of coffee, and for different types of beverages (cappuccino, lattes, tea etc) to ensure that the flavouring is not over-powering or insufficient for the base beverage. Consistent dosing is further complicated when several flavours are added to the same beverage, as different flavours can overpower others. For example, mint flavouring can easily overpower a vanilla flavouring of the same quantity. Hence, consistent and accurate dosing of flavourings cannot be achieved when a server is responsible for manually preparing a flavoured beverage.
Another factor for consideration is the concentrated flavouring itself. Manufacturers and retailers prefer to use concentrated flavouring with minimal carrier, as the carrier can affect the flavouring and taste of the flavoured beverage, and the additional volume contributed by the carrier increases shipping costs of the flavouring. Thus, the highly concentrated flavouring to be added can be in the order of several milliliters, depending on the type and size of beverage. Due to the highly concentrated nature of the concentrated flavouring, accuracy of the dispense becomes critical since the absence or addition of a fraction of a milliliter can significantly affect the taste of the beverage.
Known dispensing machines include simple gravity fed valves, peristaltic pumps, pressurized systems and displacement pumps, for dispensing fluids. However, none of these types of machines are suitable for dispensing the very small volumes of concentrated flavouring fluid desired by the industry. Primarily, these types of machines are not suitable for dispensing small quantities of fluids of varying viscosity, particularly high viscosity syrups having centepoise values of close to 4000.
One novel dispensing system is disclosed in commonly owned U.S. patent application Ser. No. 10/830,033, filed on Apr. 23, 2004. The dispensing system includes a cabinet for containing a multitude of displacement pumps, where each displacement pump is in direct fluid communication with a respective storage tank, and a control panel having a programmable microprocessor mounted to the cabinet for receiving user selections and controlling each individual pump. Each displacement pump includes a stepper motor in engagement with a threaded drive rod for advancing a piston by any one of several predetermined distances to dispense a corresponding volume of fluid. The control panel receives a valid user selection for actuating one or more pumps to dispense the appropriate volume of a concentrated flavouring fluid. The microprocessor tracks the amount of fluid dispensed from each storage tank and alerts users and/or prevents further operation when reservoirs are close to empty to avoid null dispenses to customers.
Various maintenance routines can be executed through the user interface, and dispense volumes and combination dispenses can be re-programmed manually or automatically. Following is a description of the general components of this dispensing system, originally described in U.S. patent application Ser. No. 10/830,033.
The dispensing system of FIG. 1 is intended to be a commercial dispenser, for use in fast food restaurants, or similar retail environments. FIG. 1 is an isometric view of dispensing machine 100, with an array of pump assemblies positioned within cabinet 102, having a door panel 104. As shown in FIG. 1, there are flexible tubes located between nozzle cap 106 and each displacement pump.
FIG. 2 is a side view of one pump assembly 110 used in the system of FIG. 1 to illustrate the configuration of the displacement pump 112 and its corresponding storage tank 114. Storage tank 114 can be constructed of molded plastic material, metal, or any suitable liquid impermeable material, for storing concentrated flavouring fluid. The storage tank is preferably constructed of a rigid material. The tank is filled by removing tank cap 116 and pouring concentrated flavouring fluid into the open aperture (not shown). The stored concentrated flavouring fluid is provided to displacement pump 112 through a short tank nozzle in fluid communication with the storage tank 114 that extends from the bottom of storage tank 114 and into a check valve retainer 118. The short tank nozzle is preferably constructed of the same material as the storage tank 114, and preferably provided in the same die mold as the storage tank 114. Tank cap 116 preferably includes an O-ring and a one way check valve to allow entry of air into the volume of the storage tank 114 as concentrated fluid is drawn, but prevents vapours from escaping and potentially contaminating flavours stored in the other storage tanks 114.
FIG. 3 shows components of displacement pump 112, and in particular, details of the piston 130 and threaded drive rod 132. Piston 130 is fixed to a piston seal 134 made of Santoprene™ a type of thermoplastic elastomer available from Advanced Elastomer Systems or tetrafluoroethylene available from Dupont, where the piston seal 134 is dimensioned to sealingly engage the inner surface of cylinder tube chamber 136. Piston seal 134 has a wide contact edge, preferably a width to provide structural/mechanical stability of the edge under load. In the present embodiments, the width of piston seal 134 can be between 2 to 3.5 mm. However, the selection of the width can be based on the desired sealing surface, frictional wear, and force required to drive the piston seal 134. In contrast, a narrow contact edge can bow as the piston seal 134 is advanced, resulting in potential leakage of fluid into the space behind the piston seal 134. Due to the small volumes of fluid to be dispensed, small amounts of leakage can contribute to inaccurate dispenses. In addition to inaccurate dispenses, the aromatic impact of the leaked fluid is undesired, and reliability of the displacement pump may be affected. More specifically, the leaked fluid can come into contact with threaded drive rod 132, rod guide 138 and guide tube 140, which can affect their operation. Unfortunately, rebuild or replacement of the displacement pump is required for correcting this problem. Therefore, the relatively wide contact edge is selected to prevent any bowing of the contact edge during operation, and potential leakage of fluid from cylinder tube chamber 136.
An end of threaded drive rod 132 is fixed to a recess in piston 130 via spring pin 142 that extends through the walls of piston 130 and threaded drive rod 132. Also fixed to threaded drive rod 132 is a rod guide 138. Rod guide 138 slips over threaded drive rod 132 and is fixed by spring pin 144 which extends through the walls of rod guide 138 and threaded drive rod 132. The rod guide 138 is fixed to threaded drive rod 132 at a position such that it only travels within guide tube 140.
Additional components of displacement pump 112 include O-rings, such as O-ring 146 for sealing the interface between one way check valve 148 within cylinder front flange 150, check valve retainer 151, gasket face seal 152 for sealing the interface between cylinder tube chamber 136 and cylinder front flange 150, and nuts 154 and 156 for tightening threaded rods 158 and holding the displacement pump components together in a torqued compression, and a cylinder rear flange 157. Cylinder front flange 150 includes a passage for receiving check valve nozzle 159, for receiving a capillary tube.
Stepper motor 160 is a commercially available product having a face that mates with guide tube flange 162. Those of skill in the art will understand that stepper motor 160 includes a stator and a rotor that engages, rotates threaded drive rod 132 in a worm gear relationship to translate rotational movement of the rotor into linear motion of the threaded drive rod 132. Therefore, the threaded drive rod 132 is advanced or withdrawn depending on the clockwise or counter-clockwise rotation of the rotor. Stepper motor operation is well known to persons of skill in the art. Generally, the stepper motor rotates by predetermined step sizes in response to electrical input signals. Hence, the travel distance of a drive rod having a known thread pattern can easily be determined and controlled.
The aforementioned dispenser is typically operated and maintained by trained personnel, typically staff of a restaurant or service counter. While operation of the dispenser is straightforward, maintenance of the dispenser can be cumbersome. In particular, when the storage tank 114 runs empty, the user will need to pull out the displacement pump 112 containing the empty storage tank, and re-fill the tank from another container. Preferably, this is done without spillage during the transfer, which may be difficult during peak service periods when the re-fill must be done rapidly. Of course, any spillage should be cleaned up for hygiene purposes. Furthermore, the user may initiate pre-programmed clean and prime operations for the dispensing unit if a different flavouring is to be used for a displacement pump.
The aforementioned dispenser can be used in a self-serve environment. For example, customers purchasing a beverage in a convenience store can choose to add a desired flavouring by pushing the appropriate buttons on the user interface. This is convenient for the convenience store clerk who is typically alone and does not have time to service the client. However when it comes time to refill the tank, the clerk will not have sufficient training or time to properly refill the tank, resulting in spillage that is not typically cleaned. The relative complexity of refilling the tanks of the dispenser, and/or risk of spilling concentrated fluid, may deter convenience store clerks from maintaining the machine.
It is, therefore, desirable to provide a dispensing machine that provides a simple and rapid flavour refilling system while minimizing fluid spillage during a refill operation.